This invention relates to cryptographic systems, and more particularly, to document imaging systems with identity-based encryption capabilities.
Cryptographic systems are used to provide secure communications services such as secure email services. For example, in a secure email system, a secure email message may be conveyed from a sender to a recipient over the Internet.
With symmetric key cryptographic systems, the sender of a message uses the same key to encrypt the message that the recipient of the message uses to decrypt the message. Symmetric-key systems require that each sender and recipient exchange a shared key in a secure manner.
With public-key cryptographic systems, two types of keys are used—public keys and private keys. Senders may encrypt messages using the public keys of the recipients. Each recipient has a private key that is used to decrypt the messages for that recipient.
One public-key cryptographic system that is in use is the RSA cryptographic system. Each user in this system has a unique public key and a unique private key. A sender may obtain the public key of a given recipient from a key server over the Internet. To ensure the authenticity of the public key and thereby defeat possible man-in-the-middle attacks, the public key may be provided to the sender with a certificate signed by a trusted certificate authority. The certificate may be used to verify that the public key belongs to the intended recipient of the sender's message. Public key encryption systems such as the RSA system that use this type of traditional approach are referred to as PKE cryptographic systems.
Identity-based-encryption (IBE) systems have also been proposed. As with PKE cryptographic systems, a sender in an IBE system may encrypt a message for a given recipient using the recipient's public key. The recipient may then decrypt the message using the recipient's corresponding private key. The recipient can obtain the private key from a private key generator.
Unlike PKE schemes, IBE schemes generally do not require the sender to look up the recipient's public key. Rather, a sender in an IBE system may generate a given recipient's IBE public key based on known rules. For example, a message recipient's email address or other identity-based information may be used as the recipient's public key, so that a sender may create the IBE public key of a recipient by simply determining the recipient's email address.
Although senders of IBE-encrypted messages need not look up a recipient's public key as with PKE schemes, senders must obtain so-called IBE public parameter information that is associated with the recipient's IBE private key generator. The IBE public parameter information is used as an ancillary input to the sender's IBE encryption algorithm and works in conjunction with the IBE public key of the recipient to ensure that the message is encrypted properly.
Individual users in an IBE system can encrypt messages locally on their computers using an IBE encryption engine that is implemented as a plug-in to an email client. In environments in which users are networked at an organization, a gateway may be used to encrypt outgoing messages for the users.
Traditional arrangements such as these do not necessarily provide desired levels of security. For example, in situations in which a user scans a document on a network-attached scanner, the communications path between the scanner and the user's computer may not be secure. This may result in documents stored in the scanner's memory or on the network that are not in encrypted form. Moreover, if a user desires to email a document directly from an email-enabled scanner, the document may be vulnerable to interception.
It would therefore be desirable to be able to provide ways in which to improve data security in communications systems, particularly in systems in which documents are created using equipment such as scanners.